Generally described, computing devices and communication networks can be utilized to exchange information. In a common application, a computing device can request content from another computing device via the communication network. For example, a user at a personal computing device can utilize a software browser application, typically referred to as a browser software application, to request a Web page from a server computing device via the Internet. In such embodiments, the user computing device can be referred to as a client computing device and the server computing device can be referred to as a content provider.
With reference to an illustrative example, a requested Web page, or original content, may be associated with a number of additional resources, such as images or videos, that are to be displayed with the Web page. In one specific embodiment, the additional resources of the Web page are identified by a number of embedded resource identifiers, such as uniform resource locators (“URLs”). In turn, software on the client computing devices, such as a browser software application, typically processes embedded resource identifiers to generate requests for the content. Accordingly, in order to satisfy a content request, one or more content providers will generally provide client computing devices data associated with the Web page as well as the data associated with the embedded resources.
Once the client computing device obtains the Web page and associated additional resources, the content may be processed in a number of stages by the software browser application or other client computing device interface. For example, and with reference to the above illustration, the software browser application may parse the Web page to process various HTML layout information and references to associated resources, may identify and process Cascading Style Sheets (“CSS”) information, may process and instantiate various JavaScript code associated with the Web page, may construct a native object model to represent one or more components of the Web page, and may calculate various layout and display properties of the processed content for presentation to a user.
Users may define and access personal portals, which are typically composite pages containing content from a number of different content sources. The content available to add to personal portals may be limited by the portal provider. For example, content exposed by content providers in RSS feeds may be included in a personal portal. The portal provider may also develop applets or widgets that a user can add to the personal portal, and the widgets can provide access to information that is not exposed through an RSS feed. In some cases the content available to add to a portal may be limited for security reasons, because compilation of content from various sources may expose a user or client computing device to security vulnerabilities, such as cross-site scripting attacks.